The present invention relates to an auxiliary thread take-up device of a sewing machine, and in particular to a device wherein a thread suspending means is provided near a specified position where a thread guide of a take-up member is located when a needle thread loop passes between a bobbin case and a rotation stopping member thereof in order to suspend a needle thread held by the thread guide during the downward movement of the take-up member.
In a conventional sewing machine, for example as shown in FIG. 15, a thread take-up spring 4 in a spiral form is mounted in association with a spring force adjusting mechanism 3 at the turning point of a needle thread fed from the thread guide 2 of the thread take-up lever 1. Alternatively, a thread take-up spring 5 in a straight form is used in conjunction with, the spring force adjusting mechanism 3, as shown in FIGS. 16 and 17. In these cases, the thread take-up springs 4, 5 are compressed to absorb an extra amount of the needle thread when the take-up lever is elevated near its uppermost position to tighten the thread, and these springs 4 or 5 release the needle thread when the take-up lever descends. Further, these spring 4 and 5 functions to take out the needle thread smoothly from the loop taker in the middle of elevating motion of the take-up lever. The thread take-up spring 4 or 5 is a soft spring such that it will not release an extra amount of the needle thread 6 when the take-up lever is in the vicinity of the upper most position and that it will not effect thread-tightening by its spring force when stitching a thin fabric. Such a thread take-up spring was required to be capable of following the stitching speed of a sewing machine. Accordingly, the thread take-up spring was necessarily provided with the spring force adjusting mechanism 3 for adjusting its spring force.
Consequently, such a spring force adjusting mechanism made the structure of the sewing machine complicated, and since it was required to adjust the spring force adequately according to the type of a work fabric to be sewn or the type of the needle thread to be used, sewing operation necessitated substantially high skills.